[danny123]

Hello,

the tolerance of the matrix solver is set in fVsolution. This is ok for me, but under certain circumstances, I want to adapt the value, or minIter that is specified.

Is there somebody who knows, how to do that? I know how to get solverperformance, but not how to change convergence criteria within the application solver code.

Regards,

Daniel

[danny123]

I have made some progress, but I am still missing some information on the issue. The information is defined as a dictionary. I can get the information within the dictionary. I added the following code:

        const dictionary& solverControls_p = mesh.solver(p_rgh.select(pimple.finalInnerIter()));

         Info<< " before changing solverControls_p = "
            << solverControls_p
            << endl;

As an Output I get:

 solverControls_p = 
{
    solver          PCG_norm;
    preconditioner  DIC;
    tolerance       1e-05;
    relTol          0.001;
    maxIter         20000;

which is what I have specified in fvSolutions. Now I want to let's say divide "tolerance" by 10 (not changing fvSolutions though). Is this possible? How do I overwrite the value of "tolerance" in solverControls_p?

Regards,

Daniel

[alexeym]

Hi,

If you take a look at fvMesh::solver [1] documentation (which was in fact inherited from solution class), you can learn that it returns dictionary with solver settings. So the call

pEqn.solve(mesh.solver(p.select(pimple.finalInnerIter())));

Is a call to fvMatrix::sove(dictionary) [2]. And then you can look at dictionary class documentation, to learn about set method [3].

So, you either construct dictionary yourself, set desired value of tolerance (along with other linear solver parameters), and then pass this dictionary to solve method. Or you create a copy of fvMesh::solver, set desired value of the tolerance, and the pass the dictionary to solve method.

The second variant is more convenient as it takes other settings from fvSolution (you just overwrite tolerance entry of the dictionary), while using the first variant, you have to set all solver settings yourself.

1. http://foam.sourceforge.net/docs/cpp...f7779f1b8870e2
2. http://foam.sourceforge.net/docs/cpp...161fe7f7e6b9c8
3. http://foam.sourceforge.net/docs/cpp...5731ffe067b39f

[danny123]

Hi Alexey,

Thanks again for your help. Your suggestion seems logical to me, however i do not get to work. If I use the set method (method 2), I guess I will get what I want. I tried:

solverControls_p.set(tolerance,1e-06);

the compiler says that tolerance is undefined. I looked at the definition, which is I guess:

void Foam::dictionary::set(entry* entryPtr)

I tried various combinations of that type, but this did not work either. Can you help?

Regards,

Daniel

[alexeym]

Hi,

As you have used tolerance without quotes, compiler thinks it is a variable named tolerance. Do you have this variable? In general, you would use just a string "tolerance".

And you should use method [1] instead of [2]. The method is template, so you also supply type of the "tolerance" key (scalar). So the whole thing should be something like:

dictionary t(mesh.solver("field"));
t.set<scalar>("tolerance", 1e-20);
fieldEqn.solve(t);

1. http://foam.sourceforge.net/docs/cpp...2a284da0c05f4c
2. http://foam.sourceforge.net/docs/cpp...c8b1ac9e18460b

[danny123]

Hi Alexey,

Thanks, this works perfectly.

Regards,

Daniel